This proposal will focus both on the injury and recovery phases of ischemic acute renal failure. The injury phase is due to hypoxic damage to proximal tubule cells. Recent data from the PI's laboratory has established the central role for the maintenance of cellular energy supplies mainly in the form of adenosine triphosphate (ATP) and intact mitochondrial function to produce ATP in the pathogenesis of this process. Mitochondrial calcium overload appears to be a critical event in determining the degree of mitochondrial dysfunction which develops after hypoxia- reoxygenation injury. A major goal is to determine the interrelationship between phospholipase activation and the generation of reactive oxygen metabolites causing lipid peroxidation in the calcium induced mitochondrial dysfunction by utilizing isolated mitochondrial suspensions from renal cortex and well developed techniques to measure mitochondrial function and comparing it to phospholipid metabolism, free radical generation and lipid peroxidation. Recent experiments by the PI has also demonstrated an important role for glutathione in hypoxia- reoxygenation injury. Intramitochondrial glutathione is critical in maintaining mitochondrial integrity and function during potentially pathologic processes. A second goal of this proposal will determine the role of intramitochondrial glutathione in mitochondrial dysfunction following calcium loading and to determine the role of maintenance of intramitochondrial glutathione in the development of cell injury after a hypoxia- reoxygenation insult by utilizing proximal tubule segments suspensions and isolated mitochondria in vitro with various maneuvers to alter glutathione levels and to correlate these levels with quantitative metabolic parameters reflective of injury in the preparation. A final goal is to examine the recovery phase of this process which is dependent upon epithelial cell regeneration. The timing and location of these replicative events of the epithelium along the nephron will be determined. The identification of specific growth factors which are critical in this mitogenic response to injury and the assessment of changes in receptor affinity and number to these growth factors will be investigated. Studies are planned using in vivo whole kidney and in vitro proximal tubule cell culture methodology to explore these aims. Techniques to quantitate mRNA expression by dot blot hybridization, receptor kinetics, and thimidine incorporation are planned.